Liquid Biofuels. Группа авторов

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СКАЧАТЬ fluidized bed reactors is simpler. It has many advantages, such as good gas solid contact, excellent heat transfer properties, better temperature control and large heat storage capacity. Fluid bed pyrolysis offers good and consistent performance from wood, usually with a high liquid product efficiency of 60-75% by weight [58].

       1.4.2.2 Circulating Fluidized Bed and Transport Bed Reactor

      Circulating fluidized bed pyrolysis reactors have similar properties as bubble pyrolysis reactors. Compared to the bubbling fluidized bed pyrolysis reactor, steam and char are formed faster due to higher gas velocities. Thus, the char content in bio-oil is higher. Circulating fluidized bed pyrolysis reactor should provide higher process capacity, better gas solid contact [59].

Table 1.2 Types of reactors used in pyrolysis.

Reactor Type	Biomass	Temperature (°C)	Pressure (atm)	Biofuel Yield (%)	Reference
Circulating fluidized bed	Wood chips	250	138	49.9	[61]
Tubular quartz	Arthrospira platensis	450	NA	29.9	[62]
Circulating fluid bed reactor	Lignocellulosic biomass	400-600	1.6-3.3	72	[63]
Stirred semi-batch reactor	Municipal plastic wastes	400	1	76	[64]
Fluidized bed reactor	Coal and beechwood	600	NA	46	[65]
Double auger reactor	Hardwood	1061	NA	62	[66]
Downer fluidizer bed reactor	Lignocellulosic biomass	500	1	49.9	[67]
Spouted bed reactor	Lignocellulosic biomass	450	NA	58.7	[68]

       1.4.2.3 Ablative Pyrolysis Reactor

      The heat transferred from the hot reactor wall softens the raw material it contacts with under pressure. Pyrolysis moves in one direction between the biomass particles. Since the raw material is mechanically pushed forward, the remaining liquid film creates lubrication for the biomass particles. It also evaporates quickly to collect pyrolysis vapors. Pressure significantly affects the reaction rate. The advantages of the ablative pyrolysis reactor are that the particles create high pressure on the hot reactor wall due to the high relative motion and mechanical strength between the particle and the reactor wall [58].

       1.4.2.4 Rotary Cone Reactor

      Gas-solid contact was provided in the rotating conical reactor. At room temperature, biomass particles and hot sand particles are contacted near the bottom of the cone when the solids are mixed and carried up by the rotational motion of the cone. In such reactors, rapid heating and short gas retention time should be provided. Pressure is just above atmospheric levels. The initially entrained biomass enters the reactor superficially so that the particles are centrifuged against the cyclone wall, which is electrically heated to 1000 °C [59].

      1.4.3 Chemical Conversion

Basically, acid hydrolysis of hexoses, pentoses and lignin is called chemical conversion processes. Various studies are carried out on the transformation of biomass with chemical processes. Hydrolysis reactions of biomass with enzymes are rather slow compared to hydrolysis reactions with acids. Acids used in hydrolysis process are examined in two parts. The first is hydrolysis in dilute acid medium, and the second is hydrolysis using sulfuric acid [69]. In Table 1.3, the yield of biofuels obtained under different chemicals and different biomass are indicated.

      1.4.4 Electrochemical Conversion

      Biomass can be converted into electrical energy by electrochemical (electrocatalytic) oxidation of the material. This can be performed in a carbon fuel cell, using an ethanol fuel cell, a methanol fuel cell and a microbial fuel cell. Fuel can also be consumed indirectly through a fuel cell system that includes a reformer that converts biomass into a mixture of CO and H₂ before being consumed in the fuel cell [78].

Table 1.3 Biofuels as a result of chemical conversion of different chemicals and different biomass.

СКАЧАТЬ

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Biomass	Reactor Type	Temperature (°C)	Chemical	Biofuel Yield (%)	Reference
Tea factory waste	Fixed bed	400-700	KOH	24.7	[70]
Chlorella pyrenoidosa	Mini autoclave	400	Freshly deionized water	43.8	[71]
Soybean oil	5L home-made reactor	40	SnO	60	[72]
Pinewood	Autoclave	280	Pt/C	33	[73]
Empty fruit bunches	Autoclave	300	Metal chloride	22.8	[74]